Light emitting diode device

ABSTRACT

An LED device has an LED mounted on a substrate, and a transparent resin including phosphor particles for changing a color of light emitted from the LED, and sealing the LED. The transparent resin is colored by a dye at least on the surface. The dye is for correcting the changed color to a desired color.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a light emitting diode devicehaving a light emitting diode (LED) as a light source.

[0002] In recent years, there has been provided an LED device which mayemit white light, and furthermore, an LED device which may emit light ofvarious colors has been proposed.

[0003]FIG. 18 is a perspective view of a conventional LED device foremitting white light, FIG. 19 is a sectional view of the LED device.

[0004] The white light emitting LED device 120 comprises a substrate 101having a pair of terminal electrodes 102 and 103 provided on the uppersurface and the underside thereof, and an LED 105 for emitting blue orultraviolet light. The cathode of the LED 105 is connected to theelectrode 102 through an adhesive 104, and the anode is connected to theelectrode 103 by a bonding wire 106. The LED 105 and the upper surfaceof the substrate 101 are covered by a transparent resin 107. In theresin 107, yellow phosphor particles 108 are mixed.

[0005] When a driving voltage is applied to the terminal electrodes 102and 103, the LED 105 is excited to emit blue or ultraviolet light S asshown in FIG. 20.

[0006] When the blue or ultraviolet light S strikes the phosphorparticle 108, the phosphor particle emits yellow light or green lightexcited from red-green-blue S1. The mixture of the bluish light and theyellowish light takes on white light based on the wavelength conversion.

[0007]FIG. 21 is a sectional view sh wing another conventional LEDdevice 130. The same parts as the conventional LED device of FIGS. 18and 19 are identified by the same reference numerals as those of FIGS.18 and 19. In the resin 107, colored particles 109 are mixed as colorfilters.

[0008] The white light by the mixture of the bluish light and theyellowish light described above is changed by the color of the coloredparticle 109 by the subtractive color mixing. Consequently, by selectingthe color of the colored particles 109, desired color light is produced.Thus, the LED device 130 is provided to produce various color light.

[0009]FIG. 22 is a perspective view showing a back light unit forilluminating an LCD (liquid crystal display), FIG. 23 is a sectionalview of the back light unit.

[0010] The back light unit 140 comprises a pair of white light emittingLED devices 120 shown in FIG. 18, a lighting panel 142, a diffusionpanel 143, a Py prism sheet 144, a Px prism sheet 145, a reflectionplate 146, and a color LCD 147.

[0011] The lighting panel 142 is made of a transparent plastic and hasan upper surface 142 a, lower surface 142 b and front side 142 c. Thewhite light emitting LED devices 120 are mounted on an LED substrate 120b and disposed opposite the front side 142 c as edge light. Thediffusion panel 143 is disposed above the upper surface 142 a of thelighting panel 142 and the reflection plate 146 is disposed below thelower surface 142 b.

[0012] The white light emitted from the LED devices 120 enters thelighting panel 142 from the front side 142 c. The entered light isrepeatedly reflected by the upper and lower surfaces 142 a and 142 b.The light is diffusely reflected by the prism surface of the lowersurface 142 b and discharged from the upper surface 142 a. Instead ofprism, a crease or uneven surface may be used.

[0013] The discharged direction of the light is arranged in a smallrange by the diffusion panel 143, and further arranged by the prismsheets 144 and 145 in the Y and X-directions, and finally arranged inthe Z-direction. The light arranged in the Z-direction illuminates theLCD 147.

[0014] In such an illuminating device, LCDs vary in the characteristicof the color filter provided therein. Namely, the color filtercharacteristic varies with the manufacturer.

[0015] On the other hand, the chromaticity of the picture displayed onthe LCD is determined by the characteristic of the color filter and thechromaticity of the white LED device 120 illuminating the LCD. Therelationship between the characteristics will be described withreference to a drawing hereinafter.

[0016]FIG. 24 is a graph of CIE chromaticity. Here, x-coordinatedesignates proportion of R (Red), y-coordinate designates proportion ofG (Green). If proportion of B (Blue) is designated by z, there is thefollowing relationship there-between.

x+y+z=1

[0017] The point c0 in the graph is chromaticity point where the ratioof R, G and B is 1:1:1.

[0018] Coordinates of the point c0 are about x=0.33, y=0.33, z=0.33. Thepoint b0 is a coordinate point of an aim chromaticity of the white LEDdevice, and the reference letter B designates an allowable range of thepoint b0. The coordinates of the point b0 are x=0.313 and y=0.308. Thepoint d0 is a chromaticity point of the wavelength transmittance of thecolor filter of the LCD. The coordinates are x=0.352 and y=0.357. Thepoint d0 has a complementary color relation to the point b0. Thereference letter D designates a dispersion range of the point d0.

[0019] If the chromaticity of the white LED device 120 is thechromaticity at the point b0 or a value in the allowable range B, thelight from the white LED device 120 transmits the color filter having achromaticity of the point d0 or a value in the range D, so that thelight is corrected to light having a chromaticity based on the whitelight designated at the point c0.

[0020] However, the chromaticity of the light emitted from the white LEDdevice 120 varies according to dispersion of the wavelength andintensity of the light emitted from the LED 105 and dispersion of thedistribution of particles in the resin 107 of the product.

[0021] The average values of coordinates of actually manufactured whiteLED devices are x=0.295 and y=0.290, and the dispersion is σx=0.015 andσy=0.01.

[0022] The point f0 in FIG. 24 designates an average chromaticity of theab ve described products. F designates a range of the dispersion.Therefore, actual products each having chromaticity in the desired rangeB is a very small percentage of all products. Thus, the yield of thewhite LED device is very low.

SUMMARY OF THE INVENTION

[0023] An object of the present invention is to provide an LED devicehaving a constant chromaticity.

[0024] According to the present invention, there is provided a LEDdevice comprising an LED mounted on a substrate, a transparent resinincluding phosphor particles for changing a color of light emitted fromthe LED, and the transparent resin is colored by a dye at least on thesurface of the transparent resin and the dye is for correcting thechanged color to a desired color.

[0025] The dye has a color for correcting the color of the light emittedfrom the LED.

[0026] Further, the dye has a complementary color to the color of thelight emitted from the LED.

[0027] Furthermore, the present invention provides a method formanufacturing an LED device comprising the steps of mounting an LED on asubstrate, sealing the LED with a transparent resin including phosphorparticles to form an LED intermediate device, measuring chromaticity oflight from the LED device before being dyed, dyeing the transparentresin to acquire a desired color, the dye having a color for correctingthe measured chromaticity to a desired chromaticity.

[0028] The transparent resin is colored at least on the surface.

[0029] Further, the dye has a complementary color to the measuredchromaticity.

[0030] These and other objects and features of the present inventionwill become more apparent from the following detailed description withreference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0031]FIG. 1 is a perspective view of an LED device according to thepresent invention;

[0032]FIG. 2 is a sectional view of the LED device;

[0033]FIG. 3 is a sectional view showing a step for manufacturing theLED device;

[0034]FIG. 4 is a graph of chromaticity of an LED device;

[0035]FIG. 5 is an enlarged view of the graph of FIG. 4;

[0036]FIG. 6 is a graph of spectrum at chromaticity point cb andchromaticity point c1;

[0037]FIG. 7 is a graph showing spectrum of a color filter of a dye;

[0038]FIG. 8 is a graph showing spectrum of the color filter;

[0039]FIG. 9 is a graph showing spectrum of a color filter of a dye;

[0040]FIG. 10 is a graph showing spectrum of the color filter;

[0041]FIG. 11 is a graph showing spectrum of a c lor filter of a dye;

[0042]FIG. 12 is a graph showing spectrum of a color filter of a dye;

[0043]FIG. 13 is a graph showing spectrum of a color filter of a dye;

[0044]FIG. 14 is a perspective view showing a back light unit forilluminating an LCD in which a white LED complement device is used;

[0045]FIG. 15 is a sectional view of the back light unit;

[0046]FIGS. 16 and 17 are graphs of spectrum of emitted light from adevice of a second embodiment of the present invention;

[0047]FIG. 18 is a perspective view of a conventional LED device foremitting white light;

[0048]FIG. 19 is a sectional view of the conventional LED device;

[0049]FIG. 20 is a sectional view for explaining the operation of thedevice;

[0050]FIG. 21 is a sectional view showing another conventional LEDdevice;

[0051]FIG. 22 is a perspective view showing a back light unit forilluminating an LCD;

[0052]FIG. 23 is a sectional view of the back light unit; and

[0053]FIG. 24 is a graph of CIE chromaticity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0054]FIG. 1 is a perspective view of an LED device according to thepresent invention, and for emitting white light, FIG. 2 is a sectionalview of the LED device.

[0055] The light emitting LED device 21 comprises a substrate 1 having apair of terminal electrodes 2 and 3 provided on the upper surface andthe underside thereof, and a blue LED 5 for emitting blue light. Thecathode of the LED 5 is connected to the electrode 2 through an adhesive4, and the anode is connected to the electrode 3 by a bonding wire 6. Atransparent resin 7 is provided for sealing the LED 5 and the uppersurface of the substrate 1. The transparent resin 7 comprises a whitelight producing portion 10 and a colored portion 11 for producingdesired color light. In the portion 10, yellow phosphor particles or R,G or B phosphor particles 8 are mixed. In the colored portion 11,coloring dye is permeated.

[0056] A method for manufacturing the desired LED device will bedescribed hereinafter.

[0057]FIG. 3 is a sectional view showing a step for manufacturing theLED device.

[0058] The terminal electrodes 2 and 3 are formed on the upper surfaceand the underside surface of the substrate 1 by the metalizing method.The cathode of the LED 5 is connected to the electrode 2 through theadhesive 4, and the anode is connecting to the electrode 3 by thebonding wire 6. The LED 5 and the upper surface of the substrate 1 aresealed by the white light producing resin 7 including the yellowphosphor particles 8.

[0059] Thus, a whit LED device 20 is produced.

[0060] Next, the chromaticity of the white light emitted from the whiteLED device is photoelectrically measured to select LED devices which areout of a desired chromaticity. A color dye for reducing the unnecessarycolor of the light emitted from the defective LED devices is determinedand permeated in the resin 7, thereby forming the colored portion 11.Thus, a white LED completed device 21 is produced.

[0061] Next, the above described method is more particularly describedhereinafter.

[0062]FIG. 4 is a graph of chromaticity of an LED device.

[0063] The point c2 in FIG. 4 designates coordinate of an averagechromaticity of the light emitted from the white LED device 20 wherex=0.295 and y=0.290. The letter S2 designates a range of the dispersionwhere σx=0.015, σy=0.01 in a range of 3σ (N=10K). The chromaticity pointc1 is a coordinate point of an aim chromaticity of the white LED device,and the reference letter S1 designates an allowable range of the pointc1. The coordinates of the point c1 are x=0.313 and y=0.308. The rangeS1 has a dispersion of σx=0.005 and σy=0.003 about the point c1 (rangeof 3σ).

[0064] Here, a range S2 is determined as an allowable range and a whiteLED device having chromaticity in the range S2 is photoelectricallypicked up as an available device. Picked up LED devices are classifiedinto four classes a, b, c, d. Namely, the white LED device emittingbluish white light is classified into the class a, the device emittingyellowish white light is classified into the class b, the device ofreddish light is into the class c, and greenish is int the class d.

[0065] Colored dye of complementary color to the classified color isselected and transmitted in the resin 7 as described hereinafter indetail.

[0066]FIG. 5 is an enlarged view of the graph of FIG. 4. Thechromaticity point cb designates coordinates of the class a of thebluish white light, where x=0.286 and y=0.281. For the white LED deviceat the point cb, yellow dye of naphthoquinone group was selected as acomplementary color. The white LED device 20 was immersed in a dyeliquid comprising alcohol including yellow dye of 100 ppm for fifteenminutes while stirring, thereby transmitting the dye in the resin 7 toform the colored portion 11. Thus, the white LED completed device 21 wasproduced. The chromaticity of the LED device 21 was that of the desiredpoint c1. The coordinates were x=0.313 and y=0.308 of the point c1.

[0067]FIG. 6 is a graph of spectrum at chromaticity point cb andchromaticity point c1 which are shown by lines Hb and H1. In the graph,R component is a part at 625 nm, G component is a part at 560 nm and Bcomponent is a part at 450 nm.

[0068] The color correction of the bluish white light is based on thesubtractive mixture of the yellow of the dye as the subtractivecomplementary color as the following description.

[0069]FIG. 7 is a graph showing spectrum of the color of the dye. Thespectrum Fb in FIG. 7 shows the ratio of the filter characteristic R:G:Bof the yellow dye in the color d portion 11 is R:G:B=1:1:0.80. By theratio, the ratio R:G:B=0.28:0.276:0.444 of the white LED device 20,which corresponds to the chromaticity point cb, is corrected to ratioR:G:B=0.286×1:0.281×1:0.433×0.80=0.313:0.308:0.379. Thus, the white LEDdevice 21 having the chromaticity at the point c1 was produced.

[0070] Next, a white LED device 20 having a chromaticity in the range Sbwas corrected in chromaticity in a condition similar to the abovedescribed condition. As a result, the chromaticity of the light emittedfrom the LED device was corrected to a value within the range S1 aroundthe desired chromaticity at the point c1.

[0071] Chromaticity of a white LED device 20 having a chromaticity of ayellowish white was corrected. The chromaticity was in the range Syaround the chromaticity point cy of x=0.328, y=0.328 in FIG. 5. FIG. 8is a graph showing spectrum of the color filter. The spectrumcorresponding to the point cy is shown by Hy in FIG. 8.

[0072] For the white LED device at the point cy, blue dye ofanthraquinone group was selected. The white LED device 20 was immersedin a dye liquid comprising alcohol including blue dye of 100 ppm for tenminutes, thereby transmitting the dye in the resin 7 to form the coloredportion 11. Thus, a white LED completed device 21 was produced. Thecolored portion 11 has a filter characteristic shown by a referenceletter Fy in FIG. 9. The ratio of R, G, B is R:G:B=0.866:0.853:1 whichis a blue filter.

[0073] By the color correction effect, the ratio R, G, B of thchromaticity point cy (0.328:0.328:0.344) was corrected to ratioR:G:B=0.328×0.866:0.328×0.853:0.358×1=0.313:0.308:0.379. This is thechromaticity of the point c1.

[0074] Similarly, the chromaticity of LED device in the range Sy wasalso corrected to the chromaticity point in the range S1.

[0075] Next, chromaticity of a white LED device 20 having a chromaticityof a reddish white was corrected. The chromaticity was in the range Sraround the chromaticity point cr of x=0.33, y=0.30 in FIG. 5. FIG. 10 isa graph showing spectrum of the color filter. The spectrum correspondingto the point cr is shown by Hr in FIG. 10.

[0076] For the white LED device at the point cr, yellow dye of thenaphthoquinone group, and blue dye of anthraquinone group were selected.The white LED device 20 was immersed in a dye liquid comprising alcoholincluding yellow dye of 50 ppm and blue dye of 50 ppm for five minutes,thereby transmitting the dyes in the resin 7 to form the colored portion11. Thus, the white LED device 21 was produced by the summation effectof the yellow filter and the blue filter. The yellow filtercharacteristic is shown by a reference letter Fr1 in FIG. 11. The ratioof R, G, B is Ry:Gy:By=0.923:1:0.85 which is a yellow filter. The bluefilter characteristic is shown by a letter Fr2 in FIG. 11. The ratio ofA, G, B is Rb:Gb:Bb=0.858:0.858:1.

[0077] The filter characteristics are added by the subtractive mixtureto provide a total filter characteristic which is shown by the letter Frin FIG. 11. The ratio R, G, B isRf:Gf:Bf=Ry×Rb:Gy×Gb:By×Bb=0.923×0.858:0.858:0.85=0.792:0.858:0.85.

[0078] In this case, the ratio of R, G, B (0.33:0.30:0.37) in thechromaticity of the point cr was corrected by the color filter in thecolored portion 11. The ratio in the corrected chromaticity isR:G:B=0.33×0.792:0.30×0.858:0.37×0.85=0.314:0.309:0.377.

[0079] The coordinates of the chromaticity become x=0.314 and y=0.309which are nearly equal to those of the desired chromaticity c1.

[0080] A white LED device 20 having a chromaticity in the range Sr wascorrected in chromaticity in a condition similar to the above describedcondition. As a result, the chromaticity of the light emitted from theLED device was corrected to a value within the range S1 around thedesired chromaticity at the point c1.

[0081] Next, chromaticity of a white LED device 20 having a chromaticityof a greenish white was corrected. The chromaticity was in the range Sgaround the chromaticity point cg of x=0.29, y=0.315 in FIG. 5. FIG. 12is a graph showing spectrum of the color filter. The spectrumcorresponding to the point cg is shown by Hg in FIG. 12.

[0082] For the white LED device at the point cg, red dye of monoazogroup was selected. The white LED device 20 was immersed in a dye liquidcomprising alcohol including red dye of 70 ppm for ten minutes, therebytransmitting the dye in the resin 7 to form the c 1 red p rtion 11.Thus, the white LED completed device 21 was produced.

[0083] As a result, the chromaticity at the point cg was corrected to achromaticity nearly equal to that of the point c1 (x=0.313, y=0.308).Further, the chromaticity in the range Sg was corrected to achromaticity in the desired range S1. This is caused by the followingreason.

[0084] By the red dye, the filter characteristic was changed as shown byFg in FIG. 13. Namely, the ratio of filter characteristics R, G, B ischanged to red group, Rr:Gr:Br=1:0.906:0.889. Consequently, thechromaticity at the point cg is corrected. Namely, the ratio R, G, B atthe point cg is corrected from 0.29:0.315:0.395 toR:G:B=0.29×1:0.315×0.906:0.395×0.889=0.313:0.308:0.379.

[0085] As described above, if a chromaticity of a white LED device 20 isdeviated from the desired chromaticity range S1, the chromaticity can becorrected to a chromaticity in the desired chromaticity range by theselected filter provided in the colored portion 11. In general, in thecase that the ratio R, G, B in the chromaticity of a white LED device 20is R2:G2:B2, the ratio R, G, B in the desired chromaticity R1:G1:B1, andthe ratio R, G, B of the filter characteristic of the dye in the coloredlayer 11 is r:g:b,

R 2×r:G 2×g:B 2×b=R 1:G 1:B 1  (1)

[0086] If the filter characteristic r:g:b is set to satisfy the formula(1), a desired chromaticity can be provided. The filter characteristicratio R, G, B of r:g:b can be set to a desired value by selecting thecolor of the dye, kind of the solution, concentration, immersi n time.

[0087] Chromaticity of a plurality of white LED devices 20 havingvarious chromaticities were measured. Average coordinates ofchromaticity were x=0.313, y=0.308, σx=0.005, σy=0.003. The coordinateswere in the desired chromaticity range S1.

[0088]FIG. 14 is a perspective view showing a back light unit forilluminating an LCD (liquid crystal display) in which the white LEDcompleted device 21 is used, FIG. 15 is a sectional view of the backlight unit.

[0089] The back light unit 40 comprises a pair of white light emittingLED devices 21, a lighting panel 22, a diffusion panel 23, a Py prismsheet 24, a Px prism sheet 25, a reflection plate 26, and a color LCD27.

[0090] The lighting panel 22 is made of a transparent plastic and has anupper surface 22 a, lower surface 22 b and front side 22 c. The whitelight emitting LED devices 21 are mounted on an LED substrate 21 b anddisposed opposite the front side 22 c as edge light. The diffusion panel23 is disposed above the upper surface 22 a of the lighting panel 22 andthe reflection plate 26 is disposed below the lower surface 22 b.

[0091] The white light emitted from the LED devices 21 enters thelighting panel 22 from the front side 22 c. The entered light isrepeatedly reflected by the upper and lower surfaces 22 a and 22 b. Thelight is diffusely reflected by the prism surface of the lower surface22 b and discharged from the upper surface 22 a. Instead of prism, acrease or uneven surface may be used.

[0092] The discharged direction of the light is arranged in a smallrange by the diffusion panel 23, and further arranged by the prismsheets 24 and 25 in the Y and X-directions, and finally arranged in theZ-direction. The light arranged in the Z-direction illuminates the LCD27.

[0093] The chromaticity of the illuminating light is the same as that ofthe white LED device 21. The coordinates of the chromaticity are thecoordinates of the chromaticity point c1 in FIG. 5, x1=0.313, y1=0.308(z1=0.379).

[0094] The chromaticity of the transmittance of the color filter in thecolor LCD 27 is the chromaticity at a chromaticity point d0 in FIG. 4.The coordinates of the point d0 are xf=0.352, yf=0.357 (zf=0.291).

[0095] The ratio R, G, B of the illuminating light color to the LCD 27is as follows from the chromaticity (x1, y1, z1) of the white LED device21 and the chromaticity (xf, yf, zf) of the color filter in the LCD 27.

[0096]R:G:B=x1×xf:y1×yf:z1×zf=0.313×0.352:0.308×0.352:0.379×0.291=0.333:0.333:0.334

[0097] Chromaticity coordinates of the illuminating color to the LCD 27are

x=0.333, y=0.333 (z=0.334)

[0098] which are nearly white.

[0099] Although two white LED devices 21 are used, the dispersion of thechromaticities between the LED devices are σx=0.005, σy=0.003 asdescribed before, which is a very small range. Therefore, the effectwill be same even if three or more LED devices are used in the backlight unit 40.

[0100] An LED device of a second embodiment of the present inventionwill be described hereinafter. The LED device of the second embodimentis provided for emitting color light other than white light.

[0101] The construction of the LED device is the same as the firstembodiment.

[0102] An example of a method for producing an LED completed devicehaving a chromaticity point c3 (x=0.55, y=0.35, z=0.1) from an LEDdevice having a chromaticity point c2 (x=0.295, y=0.29, z=0.415) isdescribed hereinafter.

[0103] The filter characteristic of the colored layer 11 of the LEDcompleted device is calculated from the ratio of R, G, B in thechromaticities at the points c2 and c3 by using the formula (1).

[0104] In the formula (1),

R 2×r:G 2×g:B 2×b=R 1:G 1:B 1

[0105] R2:G2:B2=0.295:0.290:0.415 (corresponding to c2) is used as theratio of R, G, B of the LED intermediate device andR1:G1:B1=0.55:0.35:0.1 (corresponding to c3) is used as the ratio of R,G, B of the LED completed device.

[0106] The filter chromaticity ratio of R, G, B is r:g:b=1:0.647;0.129from the formula (1). The characteristic is shown in FIG. 17 by F2.

[0107] Next, the LED device before being dyed is immersed and mixed in adye liquid comprising alcohol liquid, red dye and blue dye for a propertime and at a temperature, so that the filter characteristic ratiobecomes r:g:b=1:0.647:0.129. Thus, an LED completed device is produced.

[0108] In FIG. 16, H2 shows a spectrum of the light emitted from the LEDdevice, and H3 shows a spectrum of the light emitted from the LEDcompleted device. As shown by H3, the light has red color.

[0109] The line ST in FIG. 4 shows a locus of single color lights. Inaccordance with the present invention, LED completed devices emitting aplurality of single color lights such as red, yellow, green, blue,violet and others can be produced.

[0110] In accordance with the present invention, LED devices each havinga desired chromaticity can be produced, so that the yield of the LEDdevice is increased.

[0111] While the invention has been described in conjunction withpreferred specific embodiment thereof, it will be understood that thisdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the following claims.

What is claimed is:
 1. An LED device comprising: an LED mounted on asubstrate; a transparent resin including phosphor particles for changinga color of light emitted from the LED, and sealing the LED; and a dyedyeing the sealing resin for correcting the color of the light from theLED.
 2. The device according to claim 1 wherein the dye has a color forcorrecting the color of the light from the LED to acquiring a desiredcolor of light.
 3. The device according to claim 1 wherein the dye has acomplementary color to the color of the light emitted from the LED for adesired color.
 4. The device according to claim 1 wherein at least asurface of the sealing resin is dyed by the dye.
 5. A method formanufacturing an LED device comprising the steps of: mounting an LED ona substrate; sealing the LED with a transparent resin including phosphorparticles to form an LED device before being dyed; measuringchromaticity of light from the LED device before being dyed; dyeing thesealing resin by a dye having a color for correcting the measuredchromaticity to a desired color.
 6. The method according to claim 5wherein dyeing of the transparent resin is controlled by at least onecondition selected from the concentration of the dye, the temperature ofa liquid in which a dye is put, and the time in soaking the LED devicebefore being dyed in the liquid containing the dye.